Circuit module including a duplexer mounted on a circuit substrate having a specified second ground path

ABSTRACT

A circuit module includes a duplexer and a circuit substrate. A first signal path connects a first external electrode to a second external electrode. A second signal path connects a third external electrode to a fourth external electrode. A third signal path connects a fifth external electrode to a sixth external electrode. A first ground path connects a seventh external electrode to an eighth external electrode. A second ground path is connected to a ninth external electrode and is capacitively coupled to the second signal path.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to circuit module substrates, and more particularly, to circuit modules including a duplexer mounted thereon.

2. Description of the Related Art

Known examples of existing circuit modules include an antenna switch module disclosed in Japanese Unexamined Patent Application Publication No. 2006-295530. In this antenna switch module, a first reception signal and a second reception signal which have been received through an antenna and which are based on different communication systems are separated. The separated first and second reception signals are transmitted within a multilayer dielectric medium.

With the antenna switch module disclosed in Japanese Unexamined Patent Application Publication No. 2006-295530, there is a need for reducing undesirable interference generated between the first and second reception signals.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention reduce undesirable interference generated among a plurality of types of signals in a circuit module on which a duplexer that separates a plurality of types of signal is mounted.

A circuit module according to a first preferred embodiment of the present invention is a circuit module that includes a duplexer and a circuit substrate on which the duplexer is mounted. The duplexer includes a duplexer main body; first, second and third external electrodes and a plurality of duplexer ground external electrodes provided on the duplexer main body; a first filter that outputs a signal input at the first external electrode to the second external electrode; a second filter that outputs a signal input at the third external electrode to the first external electrode; a ground conductor that is connected to the duplexer ground external electrodes and that is maintained at a ground potential. The circuit substrate includes a substrate main body; fourth, fifth and sixth external electrodes and a plurality of substrate top surface ground external electrodes that are provided on the substrate main body and that are respectively connected to the first, second and third external electrodes and the plurality of the duplexer ground external electrodes; seventh, eighth and ninth external electrodes and a substrate bottom surface ground external electrode provided on the substrate main body; a first signal path that connects the fourth external electrode to the seventh external electrode, a second signal path that connects the fifth external electrode to the eighth external electrode, and a third signal path that connects the sixth external electrode to the ninth external electrode; a first ground path that connects a portion of the plurality of the substrate top surface ground external electrodes to the substrate bottom surface ground external electrode; and a second ground path that is connected to the substrate top surface ground external electrode which is not connected to the substrate bottom surface ground external electrode and that is electromagnetically coupled to the second signal path or the third signal path.

A circuit module according to a second preferred embodiment of the present invention is a circuit module that includes a duplexer and a circuit substrate on which the duplexer is mounted. The duplexer includes a duplexer main body; first, second and third external electrodes and a plurality of duplexer ground external electrodes provided on the duplexer main body; a first filter that outputs a signal input at the first external electrode to the second external electrode; a second filter that outputs a signal input at the third external electrode to the first external electrode; a ground conductor that is connected to the duplexer ground external electrodes and that is maintained at a ground potential. The circuit substrate includes a substrate main body; fourth, fifth and sixth external electrodes and a plurality of substrate top surface ground external electrodes that are provided on the substrate main body and that are respectively connected to the first, second and third external electrodes and the plurality of the duplexer ground external electrodes; seventh, eighth and ninth external electrodes and a substrate bottom surface ground external electrode provided on the substrate main body; a first signal path that connects the fourth external electrode to the seventh external electrode, a second signal path that connects the fifth external electrode to the eighth external electrode, and a third signal path that connects the sixth external electrode to the ninth external electrode; a first ground path that connects a portion of the plurality of the substrate top surface ground external electrodes to the substrate bottom surface ground external electrode; and a second ground path that is connected to the substrate top surface ground external electrode which is not connected to the substrate bottom surface ground external electrode and that is coupled to the second signal path or the third signal path through a phase unit.

According to various preferred embodiments of the present invention, in a circuit module on which a duplexer that separates a plurality of types of signal is mounted, undesirable interference generated among the plurality of types of signal is significantly reduced and prevented.

The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are external perspective views of a circuit module.

FIG. 2 is a circuit diagram of a circuit module.

FIG. 3 is an exploded view of a circuit substrate of a circuit module.

FIG. 4 is a graph illustrating pass band characteristics for a reception signal.

FIG. 5 is a graph illustrating pass band characteristics for a transmission signal.

FIG. 6 is a graph illustrating isolation characteristics.

FIG. 7 is a magnified view of the graph illustrated in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, circuit modules according to preferred embodiments of the present invention will be described with reference to the drawings.

First, the configuration of a circuit module is described with reference to the drawings. FIGS. 1A and 1B are external perspective views of a circuit module 1. FIG. 1A is a diagram of the circuit module 1 viewed from above, and FIG. 1B is a diagram of the circuit module 1 viewed from below. FIG. 2 is a circuit diagram of the circuit module 1. FIG. 3 is an exploded view of a circuit substrate 10 of the circuit module 1.

Hereinafter, the stacking direction of the circuit substrate 10 is defined as the z-axis direction. When the circuit substrate 10 is viewed in plan from the z-axis direction, a direction in which the long sides of the circuit substrate 10 extend is defined as the x-axis direction. When the circuit substrate 10 is viewed in plan from the z-axis direction, a direction in which the short sides of the circuit substrate 10 extend is defined as the y-axis direction. The x-axis direction, y-axis direction, and z-axis direction are orthogonal to one another.

The circuit module 1, which is preferably mounted on a mother board of a communication apparatus, such as a cellular phone, for example, is preferably used as a component of a transmitter/receiver circuit of a cellular phone. The circuit module 1 includes the circuit substrate 10 and a duplexer 110, as illustrated in FIGS. 1A and 1B.

First, the configuration of the duplexer 110 is described. Referring to FIGS. 1A, 1B and 2, the duplexer 110 includes a main body 112, external electrodes 114 (114 a to 114 e), SAW filters 120 a and 120 b (not illustrated in FIGS. 1A and 1B), and a ground electrode 122 (not illustrated in FIGS. 1A and 1B).

The main body 112 preferably is a multilayer body shaped like a rectangular or substantially rectangular parallelepiped, for example. For example, the main body 112 has a configuration in which, for example, the plurality of SAW filters 120 a and 120 b, each including a comb electrode provided on, for example, a crystal substrate, are mounted on a base substrate preferably formed by stacking insulator layers made of a ceramic such as alumina and are covered by a resin or a metal cap. Referring to FIGS. 1A and 1B, the external electrodes 114 are provided on a main surface of the main body 112 on the negative z-axis direction side and are preferably arranged in three rows and three columns, for example. The external electrode 114 a is provided in the second row and the third column. The external electrode 114 b is provided in the first row and the first column. The external electrode 114 c is provided in the third row and the first column. The external electrode 114 d is provided in the third row and the third column. The external electrodes 114 e are five external electrodes 114 other than the external electrodes 114 a to 114 d.

Referring to FIG. 2, the external electrode 114 a is connected to the external electrodes 114 b and 114 c by signal paths SL11 to SL13. In more detail, the signal path SL11 is connected to the external electrode 114 a. The signal paths SL12 and SL13 are connected to the signal path SL11 so as to branch from the signal path SL11 as two branch paths. The external electrodes 114 b and 114 c are respectively connected to the signal paths SL12 and SL13.

The SAW filters 120 a and 120 b, which are filters with pass bands of different frequency bands, are housed in the main body 112. In more detail, the SAW filter 120 a is provided on the signal path SL12, as illustrated in FIG. 2, and is a filter whose pass band is the frequency band (for example, 2.15 GHz) of a reception signal. The SAW filter 120 a outputs to the external electrode 114 b only high-frequency signals in the frequency band of a reception signal among high-frequency signals input at the external electrode 114 a. The SAW filter 120 b is provided on the signal path SL13, as illustrated in FIG. 2, and is a filter whose pass band is the frequency band (for example, 1.95 GHz) of a transmission signal. The SAW filter 120 b outputs to the external electrode 114 a high-frequency signals in the frequency band of a transmission signal among high-frequency signals input at the external electrode 114 c.

The ground electrode 122 is connected to the external electrodes 114 d and 114 e. The ground electrode 122 is maintained at the ground potential through the external electrodes 114 e.

The configuration of the circuit substrate 10 will now be described. Referring to FIGS. 1A, 1B and FIG. 3, the circuit substrate 10 includes a substrate main body 12 and external electrodes 14 (14 a to 14 e) and 16 (16 a to 16 f).

The substrate main body 12 preferably is a multilayer body shaped like a rectangular or substantially rectangular parallelepiped, for example, and has a configuration in which insulator layers 18 (18 a to 18 i) are stacked, as illustrated in FIG. 3. Hereinafter, a main surface of the substrate main body on the positive z-axis direction side is defined as a main surface S1, and a main surface of the substrate main body 12 on the negative z-axis direction side is defined as a main surface S2. Further, a side of the main surface S1 on the negative y-axis direction side is defined as a side L1, a side of the main surface S1 on the negative x-axis direction side is defined as a side L2, a side of the main surface S1 on the positive x-axis direction side is defined as a side L3, and a side of the main surface S1 on the positive y-axis direction side is defined as a side L4. A side of the main surface S2 on the negative y-axis direction side is defined as a side L5, a side of the main surface S2 on the negative x-axis direction side is defined as a side L6, a side of the main surface S2 on the positive x-axis direction side is defined as a side L7, and a side of the main surface S2 on the positive y-axis direction side is defined as a side L8. Further, in the substrate main body 12, a region thereof where the duplexer 110 is mounted when viewed in plan from the z-axis direction (direction of a line normal to the main surface S1) is defined as a mounting region R.

The insulator layers 18 are preferably formed of, for example, a ceramic and are rectangular or substantially rectangular, as illustrated in FIG. 3. The insulator layers 18 a to 18 i are stacked in such a manner as to be arranged in this order from the negative z-axis direction side to the positive z-axis direction side. Hereinafter, surfaces of the insulator layers 18 on the positive z-axis direction side are called top surfaces, and surfaces of the insulator layers 18 on the negative z-axis direction side are called bottom surfaces. The main surface S1 of the substrate main body 12 is defined by the top surface of the insulator layer 18 i, and the main surface S2 of the substrate main body 12 is defined by the bottom surface of the insulator layer 18 a.

Referring to FIG. 1A, 1B and FIG. 3, the external electrodes 14 are provided on the main surface S1 (i.e., the top surface of the insulator layer 18 i) of the substrate main body 12, and are preferably arranged in three rows and three columns, for example, so as to correspond to the external electrodes 114. The external electrode 14 a is provided in the second row and the third column. The external electrode 14 b is provided in the first row and the first column. The external electrode 14 c is provided in the third row and the first column. The external electrode 14 d is provided in the third row and the third column. The external electrodes 14 e preferably are five external electrodes 14 other than the external electrodes 14 a to 14 d. As a result, when the duplexer 110 is mounted on the circuit substrate 10, the external electrodes 14 a to 14 e are respectively connected to the external electrodes 114 a to 114 e. Hence, the external electrodes 14 a to 14 e are arranged within the mounting region R when viewed in plan from the z-axis direction, as illustrated in FIGS. 1A, 1B and FIG. 3.

Referring to FIGS. 1A and 1B, the external electrodes 16 are provided on the main surface S2 (i.e., the bottom surface of the insulator layer 18 a) of the substrate main body 12, and are arranged at the center of the main surface S2 and along the periphery of the main surface S2. In more detail, the external electrode 16 a is arranged so as to be nearest to the side L8 among the sides L5 to L8, as illustrated in FIG. 3. In the present preferred embodiment, the external electrode 16 a is provided near the middle point of the side L8. Referring to FIG. 3, the external electrode 16 b is arranged so as to be nearest to the side L7 among the sides L5 to L8. In the present preferred embodiment, the external electrode 16 b is arranged near and on the positive y-axis direction side of the middle point of the side L7, among the sides L5 to L8, as illustrated in FIG. 3. Referring to FIG. 3, the external electrode 16 c is arranged so as to be nearest to the side L6 among the sides L5 to L8. In the present preferred embodiment, the external electrode 16 c is arranged near the positive y-axis direction side end of the side L6.

Referring to FIG. 3, the external electrode 16 f is arranged at the center of the main surface S2, and has a larger area than the external electrodes 16 a to 16 e. Referring to FIG. 3, the external electrodes 16 d and 16 e are arranged along the periphery of the main surface S2 together with the external electrodes 16 a to 16 c. Hence, the external electrodes 16 a to 16 e are not overlapped by the mounting region R when viewed in plan from the z-axis direction. Note that regarding the external electrodes 16 d and 16 e, only representative ones are denoted by the reference symbols in FIGS. 1A, 1B and FIG. 3 to avoid making the figures complex.

The internal configuration of the circuit substrate 10 will now be described. Referring to FIG. 3, the circuit substrate 10 includes wiring conductors 20 (20 a to 20 c), 24 (24 a, 24 b, and 24 c), ground conductors 22 (22 a and 22 b), capacitor conductors 26 (26 a and 26 b), and via hole conductors v (v1 to v41).

Referring to FIG. 3, the ground conductors 22 a and 22 b are respectively provided on the bottom surfaces of the insulator layers 18 b and 18 f and, hence, are housed in the substrate main body 12. The ground conductors 22 a and 22 b cover substantially the entire bottom surfaces of the insulator layers 18 b and 18 f and, hence, are overlapped by the mounting region R so as to include the mounting region R when viewed in plan from the z-axis direction. However, the peripheries of the ground conductors 22 a and 22 b are located slightly within the peripheries of the insulator layers 18 b and 18 f, and are not in contact with the peripheries of the insulator layers 18 b and 18 f. Further, cutouts g1 to g6 are provided at the peripheries of the ground conductors 22 a and 22 b. In addition, a hole h is provided in the ground conductor 22 b.

The via hole conductors v1 to v9 and the wiring conductor 20 a define a signal path SL1 (refer to FIG. 2) that connects the external electrode 14 a to the external electrode 16 a. Referring to FIG. 3, the via hole conductors v7 to v9 extend through the insulator layers 18 g to 18 i in the z-axis direction, and are connected to one another, thereby defining a single via hole conductor. The via hole conductor v9 is connected to the external electrode 14 a. Hence, the via hole conductors v7 to v9 are located within the mounting region R when viewed in plan from the z-axis direction.

Referring to FIG. 3, the wiring conductor 20 a is a line conductor provided on the bottom surface of the insulator layer 18 g. One end of the wiring conductor 20 a is connected to the via hole conductor v7. Hence, the one end of the wiring conductor 20 a is located within the mounting region R when viewed in plan from the z-axis direction. The other end of the wiring conductor 20 a overlaps the external electrode 16 a when viewed in plan from the z-axis direction. Hence, the other end of the wiring conductor 20 a is located outside of the mounting region R when viewed in plan from the z-axis direction. Further, the other end of the wiring conductor 20 a is located nearest to the side L4 among the sides L1 to L4. In this manner, the wiring conductor 20 a extends from within the mounting region R to the outside of the mounting region R between the main surface S1 and the ground conductor 22 b when viewed in plan from the z-axis direction.

Referring to FIG. 3, the via hole conductors v1 to v6 extend through the insulator layers 18 a to 18 f, and are connected to one another, thereby defining a single via hole conductor. The via hole conductor v1 is connected to the external electrode 16 a. Hence the via hole conductors v1 to v6 are located outside of the mounting region R when viewed in plan from the z-axis direction. Further, the via hole conductor v6 is connected to the other end of the wiring conductor 20 a. Hence, the via hole conductors v1 to v6 are located nearest to the side L4 among the sides L1 to L4 when viewed in plan from the z-axis direction. Hence, the via hole conductors v1 to v6 connect the wiring conductor 20 a to the external electrode 16 a outside of the mounting region R when viewed in plan from the z-axis direction.

Further, the via hole conductors v2 and v6 respectively pass through the cutouts g1 and g4 provided in the ground conductors 22 a and 22 b. Hence, the via hole conductors v1 to v6 are not connected to the ground conductors 22 a and 22 b.

Referring to FIG. 2 and FIG. 3, the signal path SL1 configured as described above connects the external electrode 14 a to the external electrode 16 a. Further, when viewed in plan from the z-axis direction, the signal path SL1 extends from within the mounting region R to the outside of the mounting region R between the main surface S1 and the ground conductor 22 b, extends through the outside of the mounting region R, and is connected to the external electrode 16 a.

The via hole conductors v10 to v18 and the wiring conductor 20 b define a signal path SL2 (refer to FIG. 2) that connects the external electrode 14 b to the external electrode 16 b. Referring to FIG. 3, the via hole conductors v16 to v18 extend through the insulator layers 18 g to 18 i in the z-axis direction, and are connected to one another, thereby defining a single via hole conductor. The via hole conductor v18 is connected to the external electrode 14 b. Hence, the via hole conductors v16 to v18 are located within the mounting region R when viewed in plan from the z-axis direction.

Referring to FIG. 3, the wiring conductor 20 b is a line conductor provided on the bottom surface of the insulator layer 18 g. One end of the wiring conductor 20 b is connected to the via hole conductor v6. Hence, the one end of the wiring conductor 20 b is located within the mounting region R when viewed in plan from the z-axis direction. The other end of the wiring conductor 20 b overlaps the external electrode 16 b when viewed in plan from the z-axis direction. Hence, the other end of the wiring conductor 20 b is located outside of the mounting region R when viewed in plan from the z-axis direction. Further the other end of the wiring conductor 20 b is located nearest to the side L3 among the sides L1 to L4 when viewed in plan from the z-axis direction. In this manner, the wiring conductor 20 b extends from within the mounting region R to the outside of the mounting region R between the main surface S1 and the ground conductor 22 b when viewed in plan from the z-axis direction.

Referring to FIG. 3, the via hole conductors v10 to v15 extend through the insulator layers 18 a to 18 f in the z-axis direction, and are connected to one another, thereby defining a single via hole conductor. The via hole conductor v10 is connected to the external electrode 16 b. Hence, the via hole conductors v10 to v15 are located outside of the mounting region R when viewed in plan from the z-axis direction. Further, the via hole conductor v15 is connected to the other end of the wiring conductor 20 b. Hence, the via hole conductors v10 to v15 are provided nearest to the side L3 among the sides L1 to L4 when viewed in plan from the z-axis direction. Hence, the via hole conductors v10 to v15 connect the wiring conductor 20 b to the external electrode 16 b outside of the mounting region R.

Further, the via hole conductors v11 and v15 respectively pass through the cutouts g2 and g5 provided in the ground conductors 22 a and 22 b. Hence, the via hole conductors v10 to v15 are not connected to the ground conductors 22 a and 22 b.

Referring to FIG. 2 and FIG. 3, the signal path SL2 configured as described above connects the external electrode 14 b to the external electrode 16 b. Further, when viewed in plan from the z-axis direction, the signal path SL2 extends from within the mounting region R to the outside of the mounting region R between the main surface S1 and the ground conductor 22 b, extends through the outside of the mounting region R, and is connected to the external electrode 16 b.

The via hole conductors v19 to v27 and the wiring conductor 20 c define a signal path SL3 (refer to FIG. 2) that connects the external electrode 14 c to the external electrode 16 c. Referring to FIG. 3, the via hole conductors v25 to v27 extend through the insulator layers 18 g to 18 i in the z-axis direction, and are connected to one another, thereby defining a single via hole conductor. The via hole conductor v27 is connected to the external electrode 14 c. Hence, the via hole conductors v25 to v27 are located within the mounting region R when viewed in plan from the z-axis direction.

Referring to FIG. 3, the wiring conductor 20 c is a line conductor provided on the bottom surface of the insulator layer 18 g. One end of the wiring conductor 20 c is connected to the via hole conductor v25. Hence, the one end of the wiring conductor 20 c is located within the mounting region R when viewed in plan from the z-axis direction. The other end of the wiring conductor 20 c overlaps the external electrode 16 c when viewed in plan from the z-axis direction. Hence, the other end of the wiring conductor 20 c is located outside of the mounting region R when viewed in plan from the z-axis direction. Further the other end of the wiring conductor 20 c is located nearest to the side L2 among the sides L1 to L4 when viewed in plan from the z-axis direction. In this manner, the wiring conductor 20 c extends from within the mounting region R to the outside of the mounting region R between the main surface S1 and the ground conductor 22 b when viewed in plan from the z-axis direction.

Referring to FIG. 3, the via hole conductors v19 to v24 extend through the insulator layers 18 a to 18 f in the z-axis direction, and are connected to one another, thereby defining a single via hole conductor. The via hole conductor v19 is connected to the external electrode 16 c. Hence, the via hole conductors v19 to v24 are located outside of the mounting region R when viewed in plan from the z-axis direction. Further, the via hole conductor v24 is connected to the other end of the wiring conductor 20 c. Hence, the via hole conductors v19 to v24 are provided nearest to the side L2 among the sides L1 to L4 when viewed in plan from the z-axis direction. Hence, the via hole conductors v19 to v24 connect the wiring conductor 20 c to the external electrode 16 c outside of the mounting region R.

Further, the via hole conductors v20 and v24 respectively pass through the cutouts g3 and g6 provided in the ground conductors 22 ba and 22 b. Hence, the via hole conductors v19 to v24 are not connected to the ground conductors 22 a and 22 b.

Referring to FIG. 2 and FIG. 3, the signal path SL3 configured as described above connects the external electrode 14 c to the external electrode 16 c. Further, when viewed in plan from the z-axis direction, the signal path SL3 extends from within the mounting region R to the outside of the mounting region R between the main surface S1 and the ground conductor 22 b, extends through the outside of the mounting region R, and is connected to the external electrode 16 c.

The via hole conductors v33 to v41 and the ground conductors 22 a and 22 b define a ground path GL1 (refer to FIG. 2) that connects the external electrode 14 e to the external electrode 16 d. Referring to FIG. 3, the via hole conductor v33 extends through the insulator layer 18 a in the z-axis direction, and the via hole conductor v33 connects the external electrode 16 d to the ground conductor 22 a. The via hole conductor v33 is located outside of the mounting region R when viewed in plan from the z-axis direction. Note that in FIG. 3 only the representative via hole conductor v33 is denoted by the reference symbol to avoid making the figure complex.

Referring to FIG. 3, the via hole conductors v34 to v37 extend through the insulator layers 18 b to 18 e in the z-axis direction, and are connected to one another, thereby defining a single via hole conductor. The via hole conductors v34 to v37 connect the ground conductor 22 a to the ground conductor 22 b. Further, the via hole conductors v34 to v37 are located outside of the mounting region R when viewed in plan from the z-axis direction. Note that in FIG. 3 only the representative via hole conductors v34 to v37 are denoted by the reference symbols to avoid making the figure complex.

Referring to FIG. 3, the via hole conductors v38 to v41 extend through the insulator layers 18 f to 18 i in the z-axis direction, and are connected to one another, thereby defining a single via hole conductor. The via hole conductors v38 to v41 connect the ground conductor 22 b to the external electrodes 14 e. Further, the via hole conductors v38 to v41 are provided within the mounting region R when viewed in plan from the z-axis direction. Note that in FIG. 3 only the representative via hole conductors v38 to v41 are denoted by the reference symbols to avoid making the figure complex.

The ground path GL1 arranged as described above, connects the external electrode 14 e to the external electrode 16 d as illustrated in FIG. 2 and FIG. 3. Here, the external electrodes 14 e are connected to the external electrodes 114 e as illustrated in FIGS. 1A, 1B and FIG. 2. The external electrodes 114 e are connected to the ground electrode 122 of the duplexer 110. The external electrode 114 d, in addition to the external electrodes 114 e, is also connected to the ground electrode 122. The external electrode 114 d is connected to the external electrode 14 d. Hence, the ground path GL1 connects the external electrode 14 e, which is part of the external electrode 14 d and the external electrodes 14 e electrically connected to the ground electrode 122, to the external electrode 16 d.

The circuit module 1 has a configuration that reduces undesirable interference generated between a transmission signal and a reception signal. Hereinafter, this configuration will be described.

The wiring conductor 24 a and the capacitor conductor 26 a are provided on the bottom surface of the insulator layer 18 c. The capacitor conductor 26 a preferably is a rectangular or substantially rectangular conductor and defines one electrode of a capacitor C illustrated in FIG. 2. The wiring conductor 24 a is a line conductor. One end of the wiring conductor 24 a is connected to the via hole conductor v12. The other end of the wiring conductor 24 a is connected to the capacitor conductor 26 a. As described above, the via hole conductor v12 defines a portion of the signal path SL2. Hence, the one electrode (the capacitor conductor 26 a) of the capacitor C is connected to the signal path SL2 as illustrated in FIG. 2.

The wiring conductors 24 b and 24 c, the capacitor conductor 26 b, and the via hole conductors v28 to v32 define a ground path GL2 (refer to FIG. 2), which is connected to the external electrode 14 d. Referring to FIG. 3, the via hole conductors v28 and v29 extend through the insulator layers 18 e and 18 f in the z-axis direction and are connected to one another, thereby defining a single via hole conductor. Note that the ground conductor 22 b has the hole h provided therein, and the via hole conductor v29 extends through the hole h. Hence, the via hole conductors v28 and v29 are insulated from the ground conductor 22 b.

Referring to FIG. 3, the wiring conductor 24 c is a line conductor provided on the bottom surface of the insulator layer 18 g. One end of the wiring conductor 24 c is connected to the via hole conductor v29. The other end of the wiring conductor 24 c is overlapped by the external electrode 14 d when viewed in plan from the z-axis direction. The via hole conductors v30 to v32 extend through the insulator layers 18 g and 18 i and are connected to one another, thereby defining a single via hole conductor. The via hole conductor v30 is connected to the other end of the wiring conductor 24 c. The via hole conductor v32 is connected to the external electrode 14 d.

The capacitor conductor 26 b preferably is a rectangular or substantially rectangular conductor and defines the other electrode of the capacitor C illustrated in FIG. 2. Hence the capacitor conductor 26 b overlaps the capacitor conductor 26 a when viewed in plan from the z-axis direction. The wiring conductor 24 b is a line conductor. One end of the wiring conductor 24 b is connected to the via hole conductor v28. The other end of the wiring conductor 24 b is connected to the capacitor conductor 26 b.

Referring to FIG. 2 and FIG. 3, the ground path GL2 configured as described above is connected to the external electrode 14 d, which is not connected to the external electrodes 16, and is capacitively coupled to the signal path SL2.

In the circuit module 1 configured as described above, a reception signal is input at the external electrode 16 a. The reception signal passes through the SAW filter 120 a, and is output to the outside of the circuit module 1 through the external electrode 16 b. Here, the SAW filter 120 b has a pass band that is the frequency band of a transmission signal and does not have a pass band that is the frequency band of a reception signal. Hence, the reception signal input at the external electrode 16 a cannot pass through the SAW filter 120 b and, hence, is not output from the external electrode 16 c.

A transmission signal is input at the external electrode 16 c. The transmission signal passes through the SAW filter 120 b and is output to the outside of the circuit module 1 through the external electrode 16 a. Here, the SAW filter 120 a has a pass band that is the frequency band of a reception signal and does not have a pass band that is the frequency band of a transmission signal. Hence, the transmission signal which has passed the SAW filter 120 b cannot pass through the SAW filter 120 a and, hence, is not output from the external electrode 16 b.

The circuit module 1 described above significantly reduces and prevents undesirable interference generated between a transmission signal and a reception signal. In more detail, as illustrated in FIG. 2 and FIG. 3, the ground path GL2 connected to the ground electrode 122 of the duplexer 110 is capacitively coupled through the capacitor C to the signal path SL2 over which a reception signal is transmitted. As a result, undesirable interference generated between a transmission signal and a reception signal is significantly reduced and prevented. The inventor of the present invention performed computer simulation described below to confirm the advantageous effects of the circuit substrate 10 according to a preferred embodiment of the present invention.

First, a model of the circuit module 1 was created as a first model. Here, the capacitance of the capacitor C was set to 0.97 pF, for example. Further, a model of the circuit module 1 without the capacitor C was created as a second model. Then, by inputting a transmission signal and a reception signal to the first model and the second model, pass band characteristics (pass band characteristics for a reception signal) between the external electrodes 16 a and 16 b, pass band characteristics (pass band characteristics for a transmission signal) between the external electrodes 16 a and 16 c, and pass band characteristics (isolation characteristics) between the external electrodes 16 b and 16 c were determined. FIG. 4 is a graph illustrating the pass band characteristics for a reception signal. FIG. 5 is a graph illustrating the pass band characteristics for a transmission signal. FIG. 6 is a graph illustrating the isolation characteristics. FIG. 7 is a magnified view of the graph illustrated in FIG. 6. In FIG. 4 to FIG. 7, the vertical axis represents insertion loss, and the horizontal axis represents frequency.

FIG. 4 and FIG. 5 show that the pass band for a transmission signal is different from the pass band for a reception signal. In other words, it can be seen that the circuit module 1 functions as a duplexer. Further, as can be seen from the graphs of the isolation characteristics illustrated in FIG. 6 and FIG. 7, the insertion loss in the first model is larger than that in the second model. This shows that the first model achieves better isolation characteristics between the external electrodes 16 b and 16 c than the second model. Hence, it can be seen that undesirable interference generated between a transmission signal and a reception signal can be significantly reduced in the first model more than in the second model.

Further, the circuit substrate 10 can significantly reduce undesirable interference generated between a transmission signal and a reception signal also due to the following reason. Specifically, in the circuit substrate 10, the ground conductors 22 a and 22 b are overlapped by the mounting region R so as to include the mounting region R when viewed in plan from the z-axis direction, as illustrated in FIG. 3. Further, when viewed in plan from the z-axis direction, the signal paths SL1 to SL3 extend to the outside of the mounting region R between the main surface S1 and the ground conductor 22 b, extend through the outside of the mounting region R, and are connected to the external electrodes 16 a and 16 c. Hence, when viewed in plan from the z-axis direction, the ground conductors 22 a and 22 b exist between any two of the signal path SL1, the signal path SL2, and the signal path SL3. The ground conductors 22 a and 22 b are maintained at the ground potential. As a result, undesirable interference generated between a transmission signal and a reception signal in the signal paths SL1 to SL3 can be reduced.

Further, undesirable interference generated between a transmission signal and a reception signal can be reduced in the circuit module 1 also due to the following reason. In detail, in the circuit module 1, the via hole conductors v1 to v6 of the signal path SL1 are located nearest to the side L4 among the sides L1 to L4, the via hole conductors v10 to v15 of the signal path SL2 are located nearest to the side L3 among the sides L1 to L4, and the via hole conductors v19 to v24 of the signal path SL3 are located nearest to the side L2 among the sides L1 to L4. Hence, the via hole conductors v1 to v6, the via hole conductors v10 to v15, and the via hole conductors v19 to v24 are close to different sides. In other words, the via hole conductors v1 to v6, the via hole conductors v10 to v15, and the via hole conductors v19 to v24 are arranged so as to be spaced apart from one another. As a result, undesirable interference generated between a transmission signal and a reception signal can be significantly reduced and prevented reduced in the signal paths SL1 to SL3.

Further, referring to FIG. 3, the via hole conductors v2, v11, and v20, which respectively extend through the insides of the cutouts g1 to g3 of the ground conductor 22 a, are surrounded by the ground conductor 22 a. The ground conductor 22 a is maintained at the ground potential. Hence, undesirable interference generated between a transmission signal and a reception signal can be significantly reduced and prevented in the signal paths SL1 to SL3.

The circuit module 1 configured as described above is not limited to the preferred embodiment described above. Hence, the circuit module 1 can be modified within the scope of the present invention.

Although the signal path SL2 preferably is capacitively coupled to the ground path GL2 in the circuit module 1 as described above, the signal path SL1 may be capacitively coupled to the ground path GL2, for example.

Although the signal path SL2 preferably is capacitively coupled to the ground path GL2 in the circuit module 1 as described above, these elements need only be electromagnetically coupled to each other. Hence, the signal path SL2 may be magnetically coupled to the ground path GL2, for example.

In the circuit module 1, the signal path SL2 may be connected to the ground path GL2 through a phase unit instead of being electromagnetically coupled to the ground path GL2. A phase unit has a configuration in which a wiring electrode is provided instead of the capacitor C illustrated in FIG. 2 and the phase is changed by adjusting the electrode length of the wiring electrode. The phase of the phase unit is, for example, 71.3° or 74.8°. Further, a balanced filter including a balanced-unbalanced conversion function may be used as the reception filter.

Note that the ground conductors 22 a and 22 b need not be provided.

Note that one end of the ground electrode 122 is connected to only the external electrodes 114 e and 114 d and the other end of the ground electrode 122 is not connected to any component, as illustrated in FIG. 2. However, the other end of the ground electrode 122 may be connected to a component within the duplexer 110 or, for example, connected to the ground terminal of the SAW filter 120 a or 120 b.

Although the single ground electrode 122 preferably is provided for the external electrodes 114 e and 114 d, the ground electrode 122 may be provided for each of the external electrodes 114 e and 114 d, for example. Further, the ground electrode 122 need only be a conductor that is maintained at the ground potential, and may be a line conductor defining the wiring or a planar conductor with a comparatively large area.

Preferred embodiments of the present invention are useful in a circuit substrate and, in particular, are advantageous in that undesirable interference generated among a plurality of types of signal is significantly reduced and prevented.

While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims. 

What is claimed is:
 1. A circuit module comprising: a duplexer; and a circuit substrate on which the duplexer is mounted; wherein the duplexer includes: a duplexer main body; first, second and third external electrodes and a plurality of duplexer ground external electrodes provided on the duplexer main body; a first filter that outputs a signal input at the first external electrode to the second external electrode; a second filter that outputs a signal input at the third external electrode to the first external electrode; a ground conductor that is connected to the duplexer ground external electrodes and that is maintained at a ground potential; and the circuit substrate includes: a substrate main body; fourth, fifth and sixth external electrodes and a plurality of substrate top surface ground external electrodes that are provided on the substrate main body and that are respectively connected to the first, second and third external electrodes and the plurality of the duplexer ground external electrodes; seventh, eighth and ninth external electrodes and a substrate bottom surface ground external electrode provided on the substrate main body; a first signal path that connects the fourth external electrode to the seventh external electrode, a second signal path that connects the fifth external electrode to the eighth external electrode, and a third signal path that connects the sixth external electrode to the ninth external electrode; a first ground path that connects a portion of the plurality of the substrate top surface ground external electrodes to the substrate bottom surface ground external electrode; and a second ground path that is connected to the substrate top surface ground external electrode which is not connected to the substrate bottom surface ground external electrode and that is electromagnetically coupled to the second signal path or the third signal path.
 2. The circuit module according to claim 1, wherein the second ground path is capacitively coupled to the second signal path or the third signal path.
 3. The circuit module according to claim 1, wherein the second ground path is magnetically coupled to the second signal path or the third signal path.
 4. The circuit module according to claim 1, wherein the duplexer includes a plurality of surface acoustic wave filters.
 5. The circuit module according to claim 4, wherein the surface acoustic wave filters have different frequency bands.
 6. The circuit module according to claim 1, wherein the circuit module is a transmitted/receiver circuit element of a communication apparatus.
 7. The circuit module according to claim 1, wherein the duplexer main body is a rectangular or substantially rectangular multilayer body.
 8. The circuit module according to claim 1, wherein substrate main body is a rectangular or substantially rectangular multilayer body.
 9. The circuit module according to claim 1, wherein the first, second, third, fourth, fifth, sixth, seventh, eighth, and ninth external electrodes are arranged in three rows and three columns.
 10. A communication apparatus including the circuit module according to claim
 1. 11. A circuit module comprising: a duplexer; and a circuit substrate on which the duplexer is mounted; wherein the duplexer includes: a duplexer main body; first, second and third external electrodes and a plurality of duplexer ground external electrodes provided on the duplexer main body; a first filter that outputs a signal input at the first external electrode to the second external electrode; a second filter that outputs a signal input at the third external electrode to the first external electrode; a ground conductor that is connected to the duplexer ground external electrodes and that is maintained at a ground potential; and the circuit substrate includes: a substrate main body; fourth, fifth and sixth external electrodes and a plurality of substrate top surface ground external electrodes that are provided on the substrate main body and that are respectively connected to the first to third external electrodes and the plurality of the duplexer ground external electrodes; seventh, eighth, and ninth external electrodes and a substrate bottom surface ground external electrode provided on the substrate main body; a first signal path that connects the fourth external electrode to the seventh external electrode, a second signal path that connects the fifth external electrode to the eighth external electrode, and a third signal path that connects the sixth external electrode to the ninth external electrode; a first ground path that connects a portion of the plurality of the substrate top surface ground external electrodes to the substrate bottom surface ground external electrode; and a second ground path that is connected to the substrate top surface ground external electrode which is not connected to the substrate bottom surface ground external electrode and that is coupled to the second signal path or the third signal path through a phase unit.
 12. The circuit module according to claim 11, wherein the second ground path is capacitively coupled to the second signal path or the third signal path.
 13. The circuit module according to claim 11, wherein the second ground path is magnetically coupled to the second signal path or the third signal path.
 14. The circuit module according to claim 11, wherein the duplexer includes a plurality of surface acoustic wave filters.
 15. The circuit module according to claim 14, wherein the surface acoustic wave filters have different frequency bands.
 16. The circuit module according to claim 11, wherein the circuit module is a transmitted/receiver circuit element of a communication apparatus.
 17. The circuit module according to claim 11, wherein the duplexer main body is a rectangular or substantially rectangular multilayer body.
 18. The circuit module according to claim 11, wherein substrate main body is a rectangular or substantially rectangular multilayer body.
 19. The circuit module according to claim 11, wherein the first, second, third, fourth, fifth, sixth, seventh, eighth, and ninth external electrodes are arranged in three rows and three columns.
 20. A communication apparatus including the circuit module according to claim
 11. 